Researchers have developed a tool that can take a supermarket chicken, and tell whether it was cage-farmed or free-range. It can also pinpoint precisely where salmon and farmed shrimp come from.
The team of German researchers recently achieved this by deciphering clues in animal genomes that can reveal unique information about the conditions in which they were raised.
These clues take the form of chemical markers that are scattered across animal DNA, small molecules that are formed by a chemical reaction called ‘DNA methylation’. The most interesting thing about these molecular markers—collectively called the ‘methylome’—and key to the researchers’ discovery, is that they can be influenced and changed by a variety environmental conditions, such as air and water quality.
This means the methylome could differ depending on how an animal was raised, as well as its genetics and development—creating something unique “like a fingerprint”, explains Frank Lyko, the study’s lead author and professor of epigenetics at the University of Heidelberg in Germany.
Other researchers have speculated about this. But this study is the first to actually compare fingerprints across commercially-important livestock species.
The researchers started with marble crayfish: these animals aren’t widely consumed, but they all have an identical genome, making them an ideal test case to determine if changing environments change their makeup too. Using a genome sequencing device that could read the methylome, they found that their patterns differed depending on whether the crayfish came from cleaner or more polluted waters. These fingerprints were also sensitive, changing over a period of time after crayfish were exposed to different environmental conditions in a set of lab experiments.
Moving on from crayfish to more commercially-relevant species, the researchers then looked at the methylomes of salmon, chicken, and shrimp. Using their identification method, the researchers could distinguish between whiteleg shrimp grown at four different aquaculture facilities: three of those facilities were all in Northern Germany, but even simple differences in their farming methods showed up in the shrimps’ methylomes, making it possible to tell them apart.
Using a dataset on salmon genomes, they could even distinguish between salmon that had come from two different ecosystems in Canada: those caught in a faster-flowing stream had a different ‘fingerprint’ to those captured in a slower-moving river.
As for the world’s most widely-consumed livestock, chicken, the researchers’ decoding skills could tell apart chickens from six different farms spread across Europe, Australia, Thailand, and the United States. What’s more, the rich genomic dataset available for chickens allowed the researchers to go further, to even distinguish factory farmed chickens from those that were free-range, thanks to the variable environmental conditions across those two scenarios.
This study suggests that species’ methylomes are a rich and untapped store of information, not just on livestock origins, but also their environmental exposures, and the conditions under which they are farmed.
If these cues were developed into a set of testable biomarkers in different livestock species, it could give us verifiable information against which to check widespread welfare and environmental claims. But deciphering these layers of information is currently time-consuming and lab-based—which is why the researchers are now working with a German company to develop a test for meat products that may be quicker and easier to use, Lyko says.
Such a tool could become increasingly valuable in our increasingly globalized world, where sustainability claims also hold more and more capital and are starting to matter more to consumers.
“Food sales are promoted by various labels: organic, sustainable, antibiotics-free, Kosher, Halal. It is presently impossible to verify these claims experimentally,” Lyko says. “Our study provides a novel and unique approach to do this.”
Venkatesh et. al. “Context-dependent DNA methylation signatures in
animal livestock.” Environmental Epigenetics. 2023.
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